Novel endogenous peptide agonists of cannabinoid receptors

Abstract

Hemopressin (Hp), a 9-residue alpha-hemoglobin-derived peptide, was previously reported to function as a CB(1) cannabinoid receptor antagonist (1) . In this study, we report that mass spectrometry (MS) data from peptidomics analyses of mouse brain extracts identified N-terminally extended forms of Hp containing either three (RVD-Hpalpha) or two (VD-Hpalpha) additional amino acids, as well as a beta-hemoglobin-derived peptide with sequence similarity to that of hemopressin (VD-Hpbeta). Characterization of the alpha-hemoglobin-derived peptides using binding and functional assays shows that in contrast to Hp, which functions as a CB(1) cannabinoid receptor antagonist, both RVD-Hpalpha and VD-Hpalpha function as agonists. Studies examining the increase in the phosphorylation of ERK1/2 levels or release of intracellular Ca(2+) indicate that these peptides activate a signal transduction pathway distinct from that activated by the endocannabinoid, 2-arachidonoylglycerol, or the classic CB(1) agonist, Hu-210. This finding suggests an additional mode of regulation of endogenous cannabinoid receptor activity. Taken together, these results suggest that the CB(1) receptor is involved in the integration of signals from both lipid- and peptide-derived signaling molecules.

Endogenous Allosteric Modulators of G Protein–Coupled Receptors

“…Figure 4D shows the effects of pepcan-12, a 12-amino-acid neuropeptide that is highly expressed in mouse brain (Gomes et al, 2009), on the binding of the orthosteric radioligand agonist [ 3 H]WIN55212-2 at the cannabinoid CB 1 receptor. In contrast to the complete inhibition of radioligand binding mediated by the orthosteric agonist CP55,940, pepcan-12 only partially inhibited specific radioligand binding at saturating concentrations, consistent with limited negative cooperativity (Bauer et al, 2012).…”

Antinociceptive Effects of Central Administration of the Endogenous Cannabinoid Receptor Type 1 Agonist VDPVNFKLLSH-OH [(m)VD-hemopressin(α)], an N-Terminally Extended Hemopressin Peptide

“…The endocannabinoid system is traditionally thought to be modulated by the lipophilic endocannabinoids. However, recent findings indicated that endocannabinoid receptors were also regulated by hemopressin peptides (Heimann et al, 2007;Gomes et al, 2009;Bomar and Galande, 2013). Hemopressin is a nonapeptide derived from the a 1 -chain of rat hemoglobin.…”

“…This nonapeptide was reported to function as an endogenous inverse agonist or antagonist of the CB 1 receptor (Heimann et al, 2007;Dodd et al, 2010). Subsequent findings revealed that three related peptides of hemopressin, mouse RVD-hemopressin(a) [(m)RVD-Hpa], mouse VD-hemopressin(a) [(m)VD-Hpa], and mouse VD-hemopressin (b), which were identified in mouse brain extracts, behaved as agonists of cannabinoid receptors with different selectivities toward CB 1 and CB 2 receptors in vitro (Gomes et al, 2009). In the G ai16 -facilitated Ca 21 release assay, both (m)RVD-Hpa and (m)VD-Hpa acted as the CB 1 agonists, whereas mouse VDhemopressin(b) functioned as a cannabinoid agonist at both CB 1 and CB 2 receptors on human embryonic kidney 293 cells coexpressing a chimeric G 16 /G i3 with either the CB 1 or CB 2 cannabinoid receptor (Gomes et al, 2009).…”

“…Subsequent findings revealed that three related peptides of hemopressin, mouse RVD-hemopressin(a) [(m)RVD-Hpa], mouse VD-hemopressin(a) [(m)VD-Hpa], and mouse VD-hemopressin (b), which were identified in mouse brain extracts, behaved as agonists of cannabinoid receptors with different selectivities toward CB 1 and CB 2 receptors in vitro (Gomes et al, 2009). In the G ai16 -facilitated Ca 21 release assay, both (m)RVD-Hpa and (m)VD-Hpa acted as the CB 1 agonists, whereas mouse VDhemopressin(b) functioned as a cannabinoid agonist at both CB 1 and CB 2 receptors on human embryonic kidney 293 cells coexpressing a chimeric G 16 /G i3 with either the CB 1 or CB 2 cannabinoid receptor (Gomes et al, 2009). However, compared with (m)RVD-Hpa, (m)VD-Hpa caused a lesser increase in intracellular Ca 21 level in cells coexpressing a chimeric G 16 /G i3 with the CB 2 receptor, implying that (m)VD-Hpa is a highly selective CB 1 agonist (Gomes et al, 2009).…”

A Novel Intracellular Peptide Derived from G1/S Cyclin D2 Induces Cell Death

“…As such, naturally occurring intracellular peptides generated by the proteasome would constitute an as yet poorly understood mechanism by which cells increase their protein network complexity and function (16). Hemopressin, the first intracellular peptide identified using this rationale (19), was shown to have cannabinoid inverse agonist action regulating food intake (20,21), whereas the natural brain hemopressins are secreted and suggested to play an important role as novel endocannabinoids (14,22).…”